1. Field of the Invention
The present invention relates generally to the field of enclosures and more specifically to switchgear enclosures which have one or more access doors and that are efficiently fabricated and assembled without the use of any externally-exposed fasteners.
2. Description of the Related Art
Metal-enclosed switchgear is well-known in the art; for example, as disclosed in U.S. Pat. No. 4,073,000. Typically, such switchgear is utilized in electrical distribution systems for large buildings, factories, industrial parks, etc. Such switchgear typically may include transformers, fuses, interrupter switches, electrical switches and other such electrical components necessary for electrical distribution systems.
The switchgear typically comprises a metal enclosure having one or more doors which provide access into the interior portions of the enclosure where the electrical components are situated. Since the electrical components are typically energized at high voltage, such metal-enclosed switchgear ordinarily has various security features including locks which are provided to hinder unauthorized access and vandalism.
Metal-enclosed switchgear of this general type is manufactured by S&C Electric Company, Chicago, Illinois as described in Descriptive Bulletin 621-30. The metal-enclosed switchgear enclosure as described therein is fabricated by the appropriate shearing, punching and folding of sheets of steel for the various walls and door portions. Next, various support members such as brackets, channels, angles and tabs are welded to the side and back sheets for appropriate supporting and mounting of the components to be housed by the particular enclosure. For example, if one enclosure contains a fuse and a switch, the support members are located in a first particular configuration. For another enclosure that contains a power-operated switch, support members are located in a second, different configuration where additional tabs are needed on the side sheets. After the various support members are welded into place, the two sidewall sheets, the rear wall, and the various front members that define the access openings are welded to each other to define the enclosure. Since the sheets are typically at least seven to eight feet in length, three to four feet wide, and of 11-gauge steel, the handling of the sheets while they are being joined by welding is a relatively complicated and time-consuming process. After the welding operation, grinding of the welded areas as well as cleaning and preparation of the steel surfaces are necessary before the painting of the enclosure. The entire enclosure is then painted. The individual enclosures are then assembled into multiple-bay line-ups. Thereafter, the fabrication of the enclosure being complete, assemblers install components and wiring personnel complete the necessary wiring to automatic controls, switch operators and the like, as required. Additionally, one or more hinged doors are added. While these metal-enclosed switchgear enclosures, as described, constitute high-quality and secure enclosures, manufacturing of the enclosures is relatively time-consuming and thus costly. Other types of enclosures are fabricated by the fastening of panels onto a frame.
Accordingly, while the enclosures of the prior art may be generally suitable for their intended purpose, it would be desirable to provide an enclosure that is efficiently fabricated from flat panels without frames or extensive welding and that includes no external fasteners.